Oracleのみ結合条件の推移律未対応
(8.0.26)
drop table tab1;
create table tab1(
col1 bigint
,col2 bigint
);
drop table tab2;
create table tab2(
col1 bigint
,col2 bigint
);
drop table tab3;
create table tab3(
col1 bigint
,col2 bigint
);
drop procedure proc1;
delimiter //
create procedure proc1(in x int)
begin
declare i int;
set i = 0;
start transaction;
while i < x do
set i = i + 1;
insert into tab1 values(
i
,floor(rand() * 100000)+1
);
insert into tab2 values(
i
,floor(rand() * 100000)+1
);
insert into tab3 values(
i
,floor(rand() * 100000)+1
);
end while;
commit;
end
//
delimiter ;
call proc1(1000000);
analyze table tab1;
analyze table tab2;
analyze table tab3;
explain analyze
select /*+ JOIN_PREFIX(t2 ,t3 ,t1) */ count(*)
from tab1 t1
inner join tab2 t2
on t1.col1 = t2.col1
inner join tab3 t3
on t1.col1 = t3.col1
;
show warnings;
→ Inner hash join (t3.col1 = t2.col1)となり、結合条件の推移律はある
(19c)
drop table tab1 purge;
create table tab1(
col1 int
,col2 int
);
drop table tab2 purge;
create table tab2(
col1 int
,col2 int
);
drop table tab3 purge;
create table tab3(
col1 int
,col2 int
);
declare
begin
for i in 1..1000000 loop
insert into tab1 values(
i
,floor(dbms_random.value(1, 100001) )
);
insert into tab2 values(
i
,floor(dbms_random.value(1, 100001) )
);
insert into tab3 values(
i
,floor(dbms_random.value(1, 100001) )
);
end loop;
end;
/
commit;
set time on
set timing on
exec dbms_stats.gather_table_stats(user,'TAB1');
exec dbms_stats.gather_table_stats(user,'TAB2');
exec dbms_stats.gather_table_stats(user,'TAB3');
explain plan for
select /*+ LEADING(t2 t3 t1) */ count(*)
from tab1 t1
inner join tab2 t2
on t1.col1 = t2.col1
inner join tab3 t3
on t1.col1 = t3.col1
;
explain plan for
select /*+ LEADING(t2 t3 t1) */ count(*)
from tab1 t1 ,tab2 t2, tab3 t3
where t1.col1 = t2.col1
and t1.col1 = t3.col1
;
select * from table(dbms_xplan.display(format=>'ALL') );
→ t2,t3の結合はMERGE JOIN CARTESIANとなり、結合条件の推移律はない★
(14)
drop table tab1;
create table tab1(
col1 bigint
,col2 bigint
);
drop table tab2;
create table tab2(
col1 bigint
,col2 bigint
);
drop table tab3;
create table tab3(
col1 bigint
,col2 bigint
);
start transaction;
insert into tab1 select
g
,floor(random() * 100000)+1
from generate_series(1,1000000) g;
commit;
start transaction;
insert into tab2 select
g
,floor(random() * 100000)+1
from generate_series(1,1000000) g;
commit;
start transaction;
insert into tab3 select
g
,floor(random() * 100000)+1
from generate_series(1,1000000) g;
commit;
\timing 1
\pset pager 0
set pg_hint_plan.debug_print=1;
show pg_hint_plan.debug_print;
analyze tab1;
analyze tab2;
analyze tab3;
/*+ Leading(( (t2 t3) t1)) */
explain
select count(*)
from tab1 t1
inner join tab2 t2
on t1.col1 = t2.col1
inner join tab3 t3
on t1.col1 = t3.col1
;
→ Hash Cond: (t2.col1 = t3.col1)となり、結合条件の推移律はある
(2019)
drop table tab1;
create table tab1(
col1 bigint not null
,col2 bigint
);
drop table tab2;
create table tab2(
col1 bigint not null
,col2 bigint
);
drop table tab3;
create table tab3(
col1 bigint not null
,col2 bigint
);
set nocount on
declare @i int;
set @i = 1;
begin transaction;
while @i <= 1000000
begin
insert into tab1 values(
@i
,floor(rand() * 100000)+1
);
insert into tab2 values(
@i
,floor(rand() * 100000)+1
);
insert into tab3 values(
@i
,floor(rand() * 100000)+1
);
set @i = @i + 1;
end
commit;
update statistics tab1;
update statistics tab2;
update statistics tab3;
set showplan_all on
go
select count(*)
from tab2 t2, tab3 t3, tab1 t1
where t1.col1 = t2.col1
and t1.col1 = t3.col1
OPTION (FORCE ORDER)
;
go
set showplan_all off
go
→ HASH:([t2].[col1])=([t3].[col1]) となり結合条件の推移律はある